Observations on the taxonomy and biology of Tylenchorhynchus macrurus (Goodey, 1932) Filipjev, 1936 and Tylenchorhynchus icarus sp.nov.

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Abstract
The large and small forms of Tylenchorhynchus macrurus are distinguished as separate species. The large form becomes T. icarus and differs from the small form, T. macrurus in the greater number of annules on the female tail, longer stylet and slimmer body. The oxygen consumption of both species is similar when assessed in terms of body surface area. Soil samples from the field indicated that (a) greatest concentrations of T. icarus occurred at about 5 cm. depth, (b) few occurred below 24 cm., the depth of the top soil, and (c) numbers of T. icarus in the top 5 cm. of soil decreased during dry periods and increased after rain. T. icarus migrates to the wet end of a moisture gradient and has maximum mobility in soil at a moisture content corresponding to field capacity and at 20° C. T. icarus survived osmotic pressure equivalent to 1 m urea for 4 days. Their oxygen consumption increased with increasing osmotic pressure but in 1 m urea there was a decline which was even more pronounced in 2 m urea. Of a population of T. icarus 35% survived for 32 weeks in soil with plants. In damp sand at 10° C, oxygen consumption was steady for 32 weeks but after 48 weeks the nematodes were dead. It is suggested that the free-living stages of plant parasitic nematodes have similar migratory habits.